Differential



May 6, 1930. F. E. CRAWFORD 1,756,939

' DIFFERENTIAL Filec'i Aug. 31, 1927 4 Sheets-Sheet 1 y 6, 1930. F. E. CRAWFORD 1,756,939

' DIFFERENTIAL Filed Aug. 31, 1927 4 Sheets-Sheet 2 v Jaye/1E7 LZ'M d. (imwrd y 30- F. a. CRAWFORD I 1,756,939

, DIFFERENTIAL v Filed Au :51, 1927 4, sheets-"sheet s y 1930. Q F. E. CRAWFORD 1,756,939

DIFFERENTIAL Patented May 6, 1930 x 'iATS -fii ii il FFEQE FRANK E. CRAWFORD, F YORK, NEBRASKA DIFFERENTIAL Application filed August 31, 1927. Serial No. 216,653.

This invention relates to the class of difwith pawls thereon, forming elements of the ierentials for automobiles which are designed several constructions illustrated in Figs. 1, 2, to permit a determined ratio of rotation of 3 and 4. the rear and power driven wheels of the auto- A reference character applied to designate a 5 niobil'es'which are controlled thereby, whether given part indicates said part throughout the 55 the difierential used be what is known as spur several figures of the drawings wherever the gear differentials, or bevelled gear wheel difsame appears.

'ferentials, and to automatically prevent a dit 1, 2, represent the non-rotatable housing of ference in the rotation of said drlven wheels the diiiierentlal, and is illustrated as consistin excess of said ratio. mg of two parts, oined by bolts 8 and nuts 4:. 60

Among the objects of this invention is to 5 represents a journal bearing for the driving obtain a differential which does not require, shai'tti, of the engine of the automobile. 7, 8, to any appreciable extent, more power to 0prepresent journal bearings in housing 1, 2, crate it than is required to operate diiierenfor the rear axles, 9, 10, of an automobile.

tials of the type commonly in use, While at the 15, 16, represent gears, which are illustrated 65 same time it automatically and positively in F '1 as rigidly secured to axles 9, 10, and limits the scope of differentiation to a prein Figs. 2 and 3 as rigidly secured on the hubs determined ratio. To obtain a diiferential of of the gear carrier, hereinafter described. 17, the class named which requires no adjustment 18, represent keys, 1), securing wheels of any of the members thereof after it is in- 15, 16, to axles 9, 10. 19, 20, represent a difstalled, and which is durable. An additional ferential gear casing, hereinafter termed the object is to obtain a diiii'erential of the class planetary ear carrier, or the carrier, which named which does not add materially to the is rotativeiy mounted on the axles 9, 10. 21, cost of constructing a differential of the com- 22, represent the hubs or" carrier 19, 20. 23

mon type, which does not require a great represent bolts and 24 nuts on said bolts, by number of additional members or parts, and means of which the two parts 19, 20, of the which is simple in construction. An addicarrier are joined together. 32 represent tional object is to obtain a differential of gears rotatably mounted in carrier 19,20, on the class named which can be substituted for shafts 25', 26.

30 differentials in common use, with no 0011- Gear 30 and 32, usually termed pinions, siderable change in the associated parts of intermesh with each other, and respectively the automobile. intermesh with gears 15, 16, this being the In the drawings referred to, Fig. 1 is a usual construction of spur gear differentials. section of a differential constructed to embody The shafts of gear pinions 30 and 82, in the 5 1y invention, oi the type known as spur gear construction embodying my invention, howdifferentials. ever, are extended beyond the side walls of Fig. 2 a section of a diiierential embodythe carrier 19, 20, and 31, 33 represent gear ing this invention of the type known as bevwheels which are rigidly mounted on the exelled gear differentials, taken on line 22 of tension or said shafts, to turn therewith. 27,

i 8, viewed as indicated by arrows. 28, represent gear wheels which are secured Fig. 3 is a section at an angle of ninety together, and are loosely mounted on axles 9,

degrees from the section illustrated in Fig. 2, 10. Gear wheel 27 intermeshes with gear showing the construction illustrated in said wheels 31, and gear wheel 28 serves as a Fig. 2. ratchet wheel or a wheel controlled against l is a sectional view of the rotatable reverse rotation by a pawl hereinafter deoperating parts of a modification of the conscribed. 29, 30 represent gear wheels which struetion illustrated in Figs.2 and 3,with the are duplicates of wheels 27, 28, and which housing of the differential and the members also, secured together. The wheel 29 inillustrated in Fig. 5, removed. termeshes with gear wheels 33, and the wheel 59 Fig. is perspective oi a rocking member 30 serves as a ratchet wheel. 34 represents and o,

keys by which the gear wheels 30, 31, 32 and 33, respectively, are illustrated as secured to shafts 25, 26. Gear pinions 30 and 31, may be integral with shafts 25, 26, if preferred. 37 represents a member which is mounted on pin or bolt 38, to rock freely thereon. 39, 40 represent pawls on member 37, which are alternately held in inoperable position by means about to be described. When one of said pawls is in inoperable position the other is in operable position, to co-act with ratchet wheels 28 and 30; the ones of said pawls in operable position depending on the direction of movement of the automobile. 41 represents a longitudinally movable bar or rod, which is provided with heads 42, 43, having, respectively inclined faces 44, 45. The bar 41 is preferably connected to the reversing gear levers of the automobile, so that when the transmission gears of the automobile are in mesh for the forward travel of the automobile said heads will be in substantially the position in which they are illustrated in Fig. 3,

with pawl 40 held by head 43 in inoperableposition. When the reverse levers of the automobile are operated to cause the automobile to travel backwards the bars 41 are moved longitudinally to cause head 41 to release pawl 40, and head 42 to maintain pawl 39 in inoperable position.

46, 47, represent a spring. Spring 46 is a duplicate of the spring 47, and one of said springs is well illustrated in Fig. 5. Springs 46, respectively, are rigidly mounted on a member 37, to press against the sides of wheels 28, 30, respectively.

In the construction illustrated in Figs. 2

1, 2, represent the non-rotatable housing of the differential, 3 and 4 the bolt and nut thereon joining the two parts 1, 2 of the housing, 5 a journal bearing for crank shaft 6 of the engine of the automobile, and 7, 8, the journal bearings for axles 9 and 10. 11, 12 represent bevelled gears of the planetary system, and 13, 14 the hubs of gears 11, 12,

respectively. Hubs 13, 14 are secured to the axles 9, 10, in the usual manner. In this construction the gear wheels 15, 16, are illustrated as rigidly secured to hubs 13, 14, but these gears can, however, be rigidly mounted on a:-..es 9, 10, the purposebeing to cause planetary gears 11, 12 andgears 15, 16, to turn in unison with said shafts or axles. 17 18 7 represent keys securing wheels 15, 16 rigidly gears identified by the same characters in F ig. 1, and hence are given the same reference characters. 31 represents a gear wheelrigidly secured on shaft 25, and 33 a similar gear, wheel which is ri idly secured on shaft 26. 27, 28 represent gear wheels which are loosely mountethto turn freely, and are illustrated as turning on hubs 21, 22 of carrier 19, 20. 29, 30, represent gear wheels which are duplicates of wheels 27, 28,'and Wheels 28, 30, respectively, function as ratchet wheels arranged to co-act with pawls 39, 40, in the same manner as in the construction illustrated in Fig. 1. Gear wheels 27 and 31 intermesh, as do gear wheels 29 and 33. 34 represents the keys which rigidly secure gear wheels 3O and 31 to shaft 25, and gear wheels 32,33, to shaft 26. 35 represents a bevelled gear of the planetary system, mounted on shaft 36, said shaft being mounted on carrier 19, 20. 37 represents a member which is mounted to rock on pin or bolt 38, and 39, 40 represent pawls on member 37 arranged to co-act with gear or ratchet wheels 28, 30, as in Fig. 1.

41 represents a longitudinallymovable bar,

and 42, 43 heads on said bar having inclined faces 44, 45, respectively. The function and action of members, 37 39, 40, 41, 42 and 43 is the same as hereinbefore described in relation to Fig. In this construction the springs 46, 47, act in the same: manner and for the same purpose as in the construction illustrated in Fig. 1. 48 represents a bevelled gear which is rigidly mounted on carrier 19,

20, as by bolts 49 and nuts 50; and 51 represents the usual bevelled gear which is rigidly mounted on shaft 6, to intermesh with gear 48.

In the construction which is illustrated in Fig. 4, 52 represent bevelled gears which are rigidly secured to gears 35, toturn therewith. 53, 54 represent shafts which are rotatively mounted in carrier 19, 29. 55, 56 represent bevelled gears which are rigidly mounted on shafts 53, respectively. 27, 28, 29, 31 and 33, respectively represent ar wheels which function the same as the 7, ar wheels identified by the same characters in Figs. 1, 2 and 3. Wheels 27, 28 are illustrated as loosely mounted on hub 21 of part 19 of the carrier 19, 29, and wheels 29, 30, are illustrated loosely mounted on hub 22 of said carrier.

'The operation of the construction which is illustrated in Fig. 1 is as follows;

Assuming the automobile to be travelling in a stra1ght course, with no slippage of the driving wheels of the automobile, the axles 9,

10, carrier 19, 20, the several gear wheels and shafts mounted in the carrier, and wheels 27, 28 and 29, 30, will rotate as a unit, and tne only power required to drive this differential over that required to drive one of common censtruction will be that due to the friction of springs 46, 47 021 the sides of wheels 30. V

uissume that wheels 15,16, each have three times the number of teeth that wheels 30 and 32 have, say fifty one and seventeen; and that to one revolution of the carrier 19, 20, the axle 9 makes one and one third revolutions. he wheel would also make one and one third revolutions, and the wheel 16 and axle 1O wouldmakc two thirds of a revolution and wheels 30 and 32 with shaft-s 25, 26, turned once around their axes. Assume wheels 31, 27, 29 and 33 have thesame number of teeth, then the rotation of shaftand wheel 31 once on the rotation of carrier 19, once around, would cause wheel 27 to remain stationary; and wheel32 andsha'lt 26 turning around once in the carrier, would cause wheel 29 to turn twice around to each rotation of the carrier. Paul l0 bcin held in an inoperable position by head 43 this accelerated rotation of wheel 29, (carrying therewith wheel 30) is permittec The above assumed turning of axle 9 one and one third revolutions and of axle 10 two thirds of a revolution, while carrier 19, 20, makes one revolution, is a ratio between said axles of'lour to two, and permits the turning of the shortest curve which the steering gear of an automobile can effect.

If, because of loss of traction the automobile wheel on axle 9 turns at a greater ratio than four to two, relative to the wheel on axle 10, the gear wheel 16 will be turned less than two thirds of a revolution, and gear wheel 30 shaft 25, and gear wheel 31 will turn more than one revolution on their axes while carrier 19, 20, makes one revolution, and the ear wheel 81 will force gears 2?, 28 in a direction reverse to the rotation of axis 9. However, a very slight rotation oi wheel 28 reverse to that ol? axle 9 will carry along therewith spring 46 and member 37, rocking said 1nemher on its pivot and bringing pawl 39 into engagement with the teeth of said gear wheel 28, thereby holding said wheel stationary and preventing rotation of wheel 31, shaft and gear thus locking gear 30 and 1a; together and forcing said gear and axle 10, to which it is secured, to turn in the same direction the carrier is turning and in a ratio of two thirds of a revolution to one revolution of said carrier.

If axle 10 is turned faster than carrier 19, 20, the sa ne operation occurs as above recit-ed,- permitting a ratio of four to two between the rear wheels of the automobile, and preventing a greater ratio. I

The operation oi the construction embodying my invention which is illustrated in Figs. 2 and 3, is the same as above described relative to Fig. 1.

The operation of the construction illus trated in Fig. 4 is as follows: Assuming planetary gears 11, 12 to have twenty four teeth, planetary gears to have twelve teeth, bevelled gears 52 to have eighteen teeth, and gears. 31, 33, and 27, 29, to-have an equal number of teeth, with bevelled gears 55, 56, having twelve teeth It axle 9 and planetary gear 111 is rotating taster than the carrier 19, 20, wheels and 52 are rotated, turning gears 55 and 56 and the shafts on which they are rigidly mounted on their axes. The wheels 56, 33: and shaft are rotated to turn wheels 29, 30, in the same direction but at a lower rateof speed, as wheel 11 is turning. hen the determined ratio is exceeded, it being with the numberof teeth assumed four to two, the operation of wheels 31, 27 and 28, the operation is the same as before described, wh el 12 being positively driven by the locking of wheels 30, 29, 33, 56, 52, 35 and 12.

In a construction embodying this invention, in the trains of gear wheels which in clude the gear wheels which are rigidly mounted on the members of the divided rear axle of an automobile, and the loosely mounted gear wheels, the rigidly mounted gear wheels are the primary driving wheels and the loosely mounted gear wheels are the final driven wheels, and the intermediate gear wheels are driven wheels when considered relative to its precedingwvheel and driving wheels when considered relative to its following wheel.

The term accelerating ratio or ratio accelerating when applied to the train of wheels which include the gear wheels which are rigidly mounted. on the members of the divided axle and the loosely mounted gear wheels, regardless of the number of intermediate gear wheels between them; but at all times including the gear pinions of the differential; means that the last driven wheel (at all times the loosely mounted gear wheel) is driven at a faster rate of revolution than its primary driving wheel, (the gear wheel which is rigidly mounted on a member of the divided axle).

' Assuming that both the rear wheels of an automobile are raised from the ground or floor and that the engine is dead.

If one wheel 01"? the automobile be turned This construction is termed accelerating.

ratio or rat-i0 accelerating; meaning that one loosely mounted wheel rotates in the direction that one of the gear wheels on one of the members of the divided axle rota-tesandthe other loosely mounted wheel rotatesin the of the divided axle;

opposite direction along with the other gear wheel which is mounted on the other member both said loosely mounted wheels rotating faster than its driving wheel on said member. 7 V

The foregoing movement relative to the driving wheels on the members of the divided axle and the corresponding loosely mounted gear wheels holds true it the rotative'carrier is rotated and one of the rear wheels of the automobile is rotated faster than the carrier. The other rear automobile Wheel must then rotate slower than said carrier. Apparently the result is that the loosely mounted wheel which is driven by the gear wheel on the member of the divided axle which is rotating faster than the carrier has its rotation accelerated; and the loosely mounted wheel which is driven by the gear wheel on the member of the divided axle which is rotated slower than the carrier has its retardation accelerated, so that it comes to a stop and is stationary before its driving wheel becomes stationary.

'I claim:

1. In a differential provided with planet ary gears, in combination a rotatably mounted diiierential gear carrier, gears loosely mounted outside said carrier, means to antomatically preventrotation of said. gears in a direction reverse to the direction of rotation of said carrier, and accelerating gear wheels rotatively mounted ,on said carrier, connecting the planetary gears of said differential with said first named gears.

2.-In a differential provided with a stationary housing, a rotatable difierential gear carrier in said housing, and planetary gears rotatably mounted in said carrier, in combination, gears loosely mounted out-side said carrier and within said housin means to automatically prevent rotation of said gears in a direction reverse to the direction of rotation of said carrier, and accelerating gear wheels rotatively mounted on said carrier, connecting the planetary gears of said differential ith said first named gears.

. 3. In a differential provided with a stationary housing, a rotatable dillerential gear carrier and planetary gears in said'housing, in combination, wheels loosely mounted outside saidcarrier and within said housing, and intermeshing accelerating gear wheels rotatively controlled'by the planet gears of the differential, connecting said planetary gears and said first named wheels, and means to hold one of said first named wheels stationary when a determined ratio of rotation between corresponding wheels of'said planetary gears is obtained.

4. In a difierential provided with a stationary housing, a rotatable differential gear carrier and planetary gears in said housing, a divided axle and gears rigidly mounted on said axle, in combination, wheels loosely mounted outside said carrier and within said housing, means to automatically prevent rotation of said wheels in a direction reverse to a determined direction of rotation of said carrier, means to control said means to automatically prevent said reverse rotation, and intermeshing gear wheels, rotatively con.- trolled by the planet gears of the difierential, connecting said planetary gears and said first named wheels. r

5. In a differential provided with a stationary housing, a rotatable differential gear carrier and planetary gears in said housing, in combination, wheels looselymounted outside said carrier and within said housing, a frame pivotally mounted on and within said housing, pawls on'said frame arranged to co-act with said first named wheels to prevent rotation thereof in a direction reverse to the direction of rotation of said carrier, means to control the direction of the pivotal movement of said frame, and inter-meshing gear wheels connecting said planetary gears and said first named wheels, said intermeshing gears arranged to control the ratioof rotation of said first named wheels to that of said planetary gears.

6. In a differential provided with a static-nary housing, arotatable differential gear carrier and planetary gearsin said housing, in combination, wheels loosely mounted outside said carrier and within said housing, a frame pivotally mounted on and within said housing, pawls on said frame arranged to co-act with said first named wheels to prevent rotation thereof in a direction reverse to the rotation of said carrier, a longitudinally movable bar, heads on said bar arranged to co-act with said frame to control the pivotal movement thereof, and interm'eshing gear wheels arranged to control the ratio of rotation of said planetary gears. V

7. A difierential unit including a rotative carrier mounted on a pair of axles driven thereby, in combination, connecting means between said axles and said carrier, loosely mounted wheels rotatable around said axles, intermeshing gears between said connecting means and said loosely mounted wheels, pawls associated'with and frictionally operable by i and o erable on said loosel mountedwheels and means operable from a remote point to hold said pawls in neutral position when said carrier is turned in a determined direction.

8. A pair of axles, a differential including a rotatable carrier and planetary gears operatively connected with said axles, and loosely mounted gear wheels associated with said carrier, in combination with automatically operable means for maintaining said loosely mounted wheels against reverse rotation, whereby when said gears act within determined ratios said differential functions and when said action reaches the determined limit oi. s: id ratios said loosely mounted gear iii) wheels function to positively drive said axles.

9. In a differential, a differential gear carrier, gears rigidly mounted on a divided axle,

gears rotatively mounted to turn loosely around said axle gears rotatively mounted on said carrier to connect said rigidly mounted and said loosely mounted gears, said connecting gears functioning, when one of said rigidly mounted gears is accelerated and the other retarded to accelerate one of said loosely mounted gears and to retard the other in a greater ratio than said rigidly mounted gears, in combination with automatic means to prevent rotation of said loosely mounted wheels reverse to the rotation of said carrier.

10. A loosely mounted wheel provided with teeth on its periphery, in combination with a frame loosely mounted on a stationary pivot, pawls on said frame, said frame being in frictional engagement with said wheel, and means independently of said frictional engagement to hold said frame with said pawls in neutral position when said wheel is revolved in a determined direction and to permit said frame to be rocked on said pivot by said frictional engagement to bring one of said pawls into engagement with said teeth when said wheel is revolved in the reverse direction.

11. In combination with a stationary housing, a pair of axles, gear wheels rigidly mounted on said axles, a rotative carrier on said axles, gear pinions rotatively mounted in said carrier, and loosely mounted gear wheels in said housing, said pinions operatively connected to said rigidly mounted wheels to control the relative rotation thereof and operatively connected to said loosely mounted wheels to drive said loosely mounted wheels, the ratio of said operative connections between said rigidly mounted wheels and said loosely mounted wheels, said connections including said pinions accelerating the rotation of the loosely mounted wheel which corresponds with the rigidly mounted wheel which is rotating faster than said carrier, and said ratio rotating the loosely mounted wheel which corresponds with the rigidly mounted wheel which is turning slower than said carrier to rotate slower than and to become stationary before said last named rigidly mounted wheel becomes stationary, and means to prevent reverse rotation of said last named loosely mounted wheel.

- FRANK E. CRAWFORD. 

